1. Technical Field
The present invention relates to an image forming system provided with a plurality of overlapping sections which overlap multiple printed sheets for making a bundle of sheets and convey the bundle of sheets toward a post processing apparatus.
2. Background Technology
An image forming apparatus, such as an electrophotographic image forming apparatus, to form images on sheets with high speed, is enabled to provide an image forming system attending a wide variety of user needs, by being connected with a post-processing apparatus having various post-processing functions.
Such the image forming system, being capable of various post-processing, can be utilized in light printing field. In that case, producing a large number of processed sheets in unit time period (hereinafter referred as productivity) is required. And in many cases, the number of processed sheets of the image forming system is determined by a capacity of the post-processing apparatus rather than a capacity of the image forming apparatus.
To be more specific, in the post-processing apparatus, since there are many cases of executing the processing by temporarily stopping the conveyance of sheet, it is required to ensure a sufficient sheet interval when continuously ejecting the sheets from the image forming apparatus. As a measure to this case, conveyance speed in the post-processing apparatus is made higher than the conveyance speed in the image forming apparatus. However, in high speed technology of recent years, since the conveyance speed of the image forming apparatus is increasing, the increase of conveyance speed in the post-processing apparatus is coming near to a limitation.
In Patent document 1 (JP 2007-156406A) an apparatus is disclosed, which is provided with an overlapping section to accumulate a plurality of sheets in an intermediate conveyance unit disposed between an image forming apparatus and a post-processing apparatus, and concurrently conveys the plurality of accumulated sheets. In this way, by concurrently conveying the plurality of sheet in the overlapped state, the time to convey the sheets to the post-processing apparatus is delayed by the number of overlapped sheets. Thus, by lengthening the substantial sheet interval without increasing the conveyance speed, total productivity of the image forming system is improved.
In order to further improve the productivity, the conveyance speed of the image forming apparatus may be increased, and in order to execute various complex post-processing, the required processing time period may be increased. In these cases, the sheet interval is required to be increased.
According to the Patent Document 1, the substantial sheet interval is increased by overlapping the plurality of sheets, and in order to further ensure the longer sheet interval, it is required to increase the number of overlapping sheets. However, increasing the overlapping sheets to increase the number of sheets to be concurrently conveyed may cause to detract the stability and alignment in sheet conveyance, which may cause degradation of quality in the bookbinding. Further, in cases of thick sheets or sheets of smooth surface, it is difficult to increase the number of overlapping sheets.
In view of these problems, an objective of the present invention is, by increasing the number of overlapping sheets, to provide an image forming system capable of maintaining the stability and quality of sheet conveyance, as well as achieving the improvement of total productivity in the image forming system.